Method and Apparatus for Chip-On Board Flexible Light Emitting Diode

ABSTRACT

A lighting device is disclosed having a plurality of LED chips mounted on a single planar flexible substrate, wherein the single planar flexible substrate is disposed in an arcuate orientation. A heat sink having an arcuate surface shaped to approximate the arcuate orientation of the flexible substrate is coupled to the flexible substrate between complementary arcuate surfaces. A luminescent coating is disposed about a top surface of the arcuate single planar flexible substrate.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/151,559 filed on Apr. 23, 2015 and entitled “Method and Apparatusfor Chip-On Board Flexible Light Emitting Diode” which is incorporatedherein by reference in its entirety.

FIELD OF THE TECHNOLOGY The present technology relates generally to thefield of light emitting diode technology and more particularly toflexible chip-on board LED technology. BACKGROUND

The present technology relates generally to Light Emitting Diode (LED)lighting components, lamps, and luminaries which can be used as lightsources in various lighting applications. Some of the significantadvantages to LED's over conventional lighting elements are theirsignificantly lower power consumption, the absence of harmful chemicals,their durability in resisting shock and vibration and their lifetime.Industrial commercial and consumer applications utilize LEDs ofdifferent power levels in various applications having different levelsof technical challenges and limitations. Higher power LEDs, appliedeither singly or in clusters, (i.e., those greater than about 10W) areused mainly in applications where high level of lumen output is requiredfrom constrained size. Typical applications are filament bulbreplacements for power levels of 40W and up, spot lights, track lightsetc. Medium power LEDs are used on applications for example wheredifferent light guides are used for producing even light output on largesurfaces.

High lumen LED assemblies are assembled on a metal core printed circuitboard (MCPCB), or on aluminum substrate, which is connected to aceramic, plastic or aluminum heat sink. Ceramic heat sinks make itpossible to use different thick film methods to manufacture theinterconnections directly on top of the heat sink. Plastic heat sinksare used mainly with MCPCBs for relatively low power solutions. Afterthe heat has been conducted through the thermal interfaces between theheat dissipating body and the PCB or MCPCB into its aluminum plate,further heat conduction is done from the bottom of the PCB, enhanced bydifferent thermal interface materials and different fastening methods,e.g. screws.

In many LED lighting applications, several high power LEDs need to beplaced in close configuration, such as flashlights, headlights and thelike. The heat generating components, their power supplies, the PCBs,the thermal interface materials, the fixing structures and heatdissipating bodies, all together dictate the achievable performancelevel in the lighting application. The resulting structure of the highpower LED is rigid and therefore limits it use and application. It istherefore desirable to have a flexible high power LED.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the technology will be apparent from thedetailed description which follows, taken in conjunction with theaccompanying drawings, which together illustrate, by way of example,features of the technology; and, wherein:

FIG. 1a is a side view illustrating one aspect of a flexible COB LEDarray in accordance with one aspect of the technology;

FIG. 1b is a top view of FIG. 1 a;

FIG. 2 is a side view of a flexible substrate in accordance with oneaspect of the technology;

FIG. 3 is a back side view of the flexible substrate of FIG. 2;

FIG. 4 is a top perspective view of the flexible substrate of FIG. 2;

FIG. 5a is a perspective view of a flexible COB LED array in accordancewith one aspect of the technology;

FIG. 5b is a top view of a flexible COB LED array in accordance with oneaspect of the technology;

FIG. 5c is a perspective view of FIG. 5 b;

FIG. 6 is a perspective view of a headlight in accordance with oneaspect of the technology;

FIG. 7a is a top view of a flexible COB LED array in accordance with onaspect of the technology;

FIG. 7b is a perspective view of a flexible COB LED array mounted on aheat sink in accordance with one aspect of the technology;

FIG. 8a is a top view of a flexible COB LED array in accordance with onaspect of the technology;

FIG. 8b is a perspective view of a flexible COB LED array mounted on aheat sink in accordance with one aspect of the technology;

FIG. 8c is a perspective view of a flexible COB LED array mounted on aheat sink in accordance with one aspect of the technology;

FIG. 9 is a top view of a base plate in accordance with one aspect ofthe technology;

FIG. 10 is a top view of an intermediate plate disposed on a base platein one aspect of the technology;

FIG. 11 is a top view of a flexible substrate in one aspect of thetechnology;

FIG. 12 is a top view of a flexible substrate disposed on theintermediate plate in one aspect of the technology;

FIG. 13 is a top view of a magnetic top plate disposed on top of theflexible substrate in one aspect of the technology;

FIG. 14 is a close up view of an LED die disposed on a contact point ofthe flexible substrate in accordance with one aspect of the technology;

FIG. 15 is a close-up view of wire connections from the LED to contactpoints on the flexible substrate in one aspect of the technology;

FIG. 16 is a close up view of a power tab of the flexible substrate inone aspect of the technology;

FIG. 17 is a perspective view of an annular heat sink in accordance withone aspect of the technology;

FIG. 18 is a perspective view of a flexible COB LED array mounted on anannular heat sink in accordance with one aspect of the technology;

FIG. 19 is a perspective view of a housing in one aspect of thetechnology;

FIG. 20 is a cut-away side view of a housing in one aspect of thetechnology;

FIG. 21 is a top view of a housing in one aspect of the technology;

FIG. 22 is a perspective view of a housing with fluorescent binder beingdisposed within the housing;

FIG. 23 is a perspective view of the housing and fluorescent binder withthe flexible COB LED array and heat sink subassembly disposed within thehousing.

DETAILED DESCRIPTION

Although the following detailed description contains many specifics forthe purpose of illustration, a person of ordinary skill in the art willappreciate that many variations and alterations to the following detailscan be made and are considered to be included herein. Accordingly, thefollowing embodiments are set forth without any loss of generality to,and without imposing limitations upon, any claims set forth. It is alsoto be understood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. Unless defined otherwise, all technical and scientific termsused herein have the same meaning as commonly understood by one ofordinary skill in the art to which this disclosure belongs.

As used in this specification and the appended claims, the singularforms “a,” “an” and “the” include plural referents unless the contextclearly dictates otherwise. Thus, for example, reference to “a layer”includes a plurality of such layers.

In this disclosure, “comprises,” “comprising,” “containing” and “having”and the like can have the meaning ascribed to them in U.S. Patent lawand can mean “includes,” “including,” and the like, and are generallyinterpreted to be open ended terms. The terms “consisting of” or“consists of” are closed terms, and include only the components,structures, steps, or the like specifically listed in conjunction withsuch terms, as well as that which is in accordance with U.S. Patent law.“Consisting essentially of” or “consists essentially of” have themeaning generally ascribed to them by U.S. Patent law. In particular,such terms are generally closed terms, with the exception of allowinginclusion of additional items, materials, components, steps, orelements, that do not materially affect the basic and novelcharacteristics or function of the item(s) used in connection therewith.For example, trace elements present in a composition, but not affectingthe compositions nature or characteristics would be permissible ifpresent under the “consisting essentially of” language, even though notexpressly recited in a list of items following such terminology. Whenusing an open ended term, like “comprising” or “including,” it isunderstood that direct support should be afforded also to “consistingessentially of” language as well as “consisting of” language as ifstated explicitly and vice versa.

The terms “first,” “second,” “third,” “fourth,” and the like in thedescription and in the claims, if any, are used for distinguishingbetween similar elements and not necessarily for describing a particularsequential or chronological order. It is to be understood that any termsso used are interchangeable under appropriate circumstances such thatthe embodiments described herein are, for example, capable of operationin sequences other than those illustrated or otherwise described herein.Similarly, if a method is described herein as comprising a series ofsteps, the order of such steps as presented herein is not necessarilythe only order in which such steps may be performed, and certain of thestated steps may possibly be omitted and/or certain other steps notdescribed herein may possibly be added to the method.

The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,”“under,” and the like in the description and in the claims, if any, areused for descriptive purposes and not necessarily for describingpermanent relative positions. It is to be understood that the terms soused are interchangeable under appropriate circumstances such that theembodiments described herein are, for example, capable of operation inother orientations than those illustrated or otherwise described herein.The term “coupled,” as used herein, is defined as directly or indirectlyconnected in an electrical or nonelectrical manner. Objects describedherein as being “adjacent to” each other may be in physical contact witheach other, in close proximity to each other, or in the same generalregion or area as each other, as appropriate for the context in whichthe phrase is used. Occurrences of the phrase “in one embodiment,” or“in one aspect,” herein do not necessarily all refer to the sameembodiment or aspect.

As used herein, the term “substantially” refers to the complete ornearly complete extent or degree of an action, characteristic, property,state, structure, item, or result. For example, an object that is“substantially” enclosed would mean that the object is either completelyenclosed or nearly completely enclosed. The exact allowable degree ofdeviation from absolute completeness may in some cases depend on thespecific context. However, generally speaking the nearness of completionwill be so as to have the same overall result as if absolute and totalcompletion were obtained. The use of “substantially” is equallyapplicable when used in a negative connotation to refer to the completeor near complete lack of an action, characteristic, property, state,structure, item, or result. For example, a composition that is“substantially free of” particles would either completely lackparticles, or so nearly completely lack particles that the effect wouldbe the same as if it completely lacked particles. In other words, acomposition that is “substantially free of” an ingredient or element maystill actually contain such item as long as there is no measurableeffect thereof.

As used herein, the term “about” is used to provide flexibility to anumerical range endpoint by providing that a given value may be “alittle above” or “a little below” the endpoint. Unless otherwise stated,use of the term “about” in accordance with a specific number ornumerical range should also be understood to provide support for suchnumerical terms or range without the term “about”. For example, for thesake of convenience and brevity, a numerical range of “about 50angstroms to about 80 angstroms” should also be understood to providesupport for the range of “50 angstroms to 80 angstroms.”

As used herein, a plurality of items, structural elements, compositionalelements, and/or materials may be presented in a common list forconvenience. However, these lists should be construed as though eachmember of the list is individually identified as a separate and uniquemember. Thus, no individual member of such list should be construed as ade facto equivalent of any other member of the same list solely based ontheir presentation in a common group without indications to thecontrary.

Concentrations, amounts, and other numerical data may be expressed orpresented herein in a range format. It is to be understood that such arange format is used merely for convenience and brevity and thus shouldbe interpreted flexibly to include not only the numerical valuesexplicitly recited as the limits of the range, but also to include allthe individual numerical values or sub-ranges encompassed within thatrange as if each numerical value and sub-range is explicitly recited. Asan illustration, a numerical range of “about 1 to about 5” should beinterpreted to include not only the explicitly recited values of about 1to about 5, but also include individual values and sub-ranges within theindicated range. Thus, included in this numerical range are individualvalues such as 2, 3, and 4 and sub-ranges such as from 1-3, from 2-4,and from 3-5, etc., as well as 1, 2, 3, 4, and 5, individually.

This same principle applies to ranges reciting only one numerical valueas a minimum or a maximum. Furthermore, such an interpretation shouldapply regardless of the breadth of the range or the characteristicsbeing described.

Reference throughout this specification to “an example” means that aparticular feature, structure, or characteristic described in connectionwith the example is included in at least one embodiment. Thus,appearances of the phrases “in an example” in various places throughoutthis specification are not necessarily all referring to the sameembodiment.

Reference in this specification may be made to devices, structures,systems, or methods that provide “improved” performance. It is to beunderstood that unless otherwise stated, such “improvement” is a measureof a benefit obtained based on a comparison to devices, structures,systems or methods in the prior art. Furthermore, it is to be understoodthat the degree of improved performance may vary between disclosedembodiments and that no equality or consistency in the amount, degree,or realization of improved performance is to be assumed as universallyapplicable.

An initial overview of the technology is provided below and specifictechnology embodiments are then described in further detail. Thisinitial summary is intended to aid readers in understanding thetechnology more quickly, but is not intended to identify key oressential features of the technology, nor is it intended to limit thescope of the claimed subject matter.

Broadly speaking, aspects of the current technology improve and makepossible the manufacture of chip onboard (COB) LEDs on a flexiblesubstrate. In one aspect of the technology, the flexible COB LED ismanufactured using a first fixture to hold a flexible substrate in placeand provide general location reference targets for aligning chipplacement, wire bonding, and gel dipping. The flexible substratecomprises conductive trace pads thereon. An adhesive is placed on theflexible substrate followed by placement of LED chips (or dies) onto theflexible substrate. This assembly is then heated for curing. The leadsof the LED dies are then wire bonded to the conductive trace pads on theflexible substrate. A second fixture is used to hold the flexiblesubstrate and bonded die sub-assembly in place while a first coating ofsilicone or other protective material is deposited on the LED dies. Thissubassembly is then heated for curing. A third fixture may be used andis placed over the sub-assembly that holds the sub-assembly immobile andprovides a flow dam as silicone gel is flooded over the LED array,followed again by a third heating step. The gel flooding may also beperformed in some cases without the need for the third fixture. Theresulting flexible COB LED array can then be used in any number ofapplications (e.g., spotlights, hand-held flashlights, headlamps,bicycle lighting, etc.) where an array having a planar geometry isapplied to an arcuate surface to provide a light source.

In another method for fabrication, the dies are fixed to the flexiblesubstrate, cured, wire bonded, cured again, selective coating ofsilicone covering the dies and wire bonds and curing in the same fashionas described above. This assembly is then mounted with thermallyconductive adhesive to a pre-shaped aluminum (or other heat conductive)structure of desired arcuate shape and inserted into a transparent ortranslucent plastic housing. A final luminescent (e.g., asilicone-phosphor or other) coating is injected into the intended spacebetween the outer wall of the transparent/translucent housing and thelight emitting surface of the flexible COB LED assembly, filling thespace. In an optional aspect, the housing is pre-loaded with a quantityof silicone-phosphor coating before the flexible COB LED assembly isplaced within the housing. Any remaining space is then filed withadditional silicone-phosphor material. In one aspect, the assembly isthen placed into a vacuum chamber to remove unwanted bubbles that may bepresent in the coating material. The entire assembly is again cured. Theresulting non-planar COB LED assembly is used as a drop-in module into afinal lighting product having a power source (i.e., battery, plug-inpower supply, etc.) coupled thereto.

With reference now to FIGS. 1a and 1b , in accordance with one aspect ofthe technology, a COB LED structure 5 is disclosed. The COB LEDstructure 5 includes a flexible substrate 10, an LED chip 30, athermally conductive binding layer 40, a circuit layer 50, a pluralityof electrical connection lines 60, a binder (e.g., clear epoxy orfluorescent adhesive) 80, and a package coating 90. It is understood,however, that not all of the above-referenced components are required ina COB LED structure used with the present technology. In addition, othercomponents may be used as suits a particular application.

In accordance with one aspect of the technology, the flexible substrate10 comprises a flexible printed circuit board (PCB) made of a flexiblepolymer, including polyamide, PTFE, acrylics, etc. Broadly speaking, aflexible PCB is an array of conductors (or conductive material) bondedto or formed with a thin dielectric film. In one aspect of thetechnology, a single-sided flexible substrate 10 is employed andcomprises a single conductive layer made of either a metal or conductivepolymer on a flexible dielectric film with component termination (orconnection) features accessible only from one side. Holes may be formedin the base film to allow component leads to pass through forinterconnection by soldering, for example. In another aspect, doubleaccess flex, also known as back bared flex are employed. These circuitsare flexible circuits having a single conductor layer that is processedso as to allow access to selected features of the conductor pattern fromboth sides. In another aspect of the technology, a double sided flexiblePCB is employed. Double-sided flex circuits are flex circuits having twoconductor layers. These flex circuits can be fabricated with or withoutplated through holes. Because of the plated through hole, terminationsfor electronic components are provided for on both sides of the circuit,thus allowing components to be placed on either side. In yet anotheraspect of the technology, a polymer thick film (PTF) circuit isemployed. PTF is a printed circuit having conductors printed onto apolymer base film. The PTF is a single conductor layer structure.

In one aspect of the technology, the base material of the flexiblepolymer film, which provides the foundation for the substrate, rangesfrom approximately 12 μm to 125 μm (½ mil to 5 mils), however, thinnerand thicker material are possible for use in different aspects of thetechnology. Thinner materials are more flexible and, for most material,the increase in stiffness is proportional to the cube of thickness.Non-limiting examples of different materials used as base filmsincluding, but not limited to polyester (PET), polyimide (PI),polyethylene napthalate (PEN), Polyetherimide (PEI), along with variousfluropolymers (FEP) and copolymers polyimide films. Adhesives are usedas the bonding medium to create the substrate. In an additional aspect,a metal foil is used as the conductive element of the flexiblesubstrate. The metal foil is the material from which the circuit pathsare etched. A wide variety of metal foils of varying thickness may beused as is known in the art.

In accordance with one aspect of the technology, the LED chip 30comprises a sapphire substrate and includes at least an N typesemiconductor layer, a semiconductor light emitting layer and a P typesemiconductor layer, which are sequentially stacked. In one aspect, theN type semiconductor layer is an N type GaN (gallium nitride) layer, thesemiconductor light emitting layer may consist of gallium nitride orindium gallium nitride, and the P type semiconductor layer is a P typeGaN layer. Further, the P type semiconductor layer and the N typesemiconductor layer are respectively connected to a positive end and anegative end of an external power source by at least one electricalconnection line 50. The thermally conductive binding layer 40 is used tobind the LED chip 30 to the flexible polymer substrate. In general, thethermally conductive binding layer 40 consists of silver paste, tinpaste, copper-tin alloy or gold-tin alloy. The circuit layer is 50formed on the flexible substrate 10 and includes a circuit pattern. Theelectrical connection lines 60 are used to connecting the LED chip 30 tothe circuit layer 50. That is, the positive and negative ends of the LEDchip 30 are respectively connected to the positive and negativeterminals of the circuit layer 50 so as to supply power to the LED chip30 and turn on the LED chip.

In one aspect, the fluorescent binder or coating 80 is deposited on theLED chip to provide the effect of fluorescence. More specifically, thefluorescent binder 80 can convert the original light generated by theLED chip 30 into the output light within the spectrum of visible lightwith a specific wavelength. For example, the original light with thespectrum of ultraviolet is converted into substantially blue (425 to 450nm) or substantially red (650 to 700 nm) light. The package coating 90is transparent, providing electrical insulation to enclose the circuitlayer 50, the electrical connection lines 60 and the fluorescent binder80. In one aspect, the package coating 90 comprises silicone gel orepoxy resin or other materials known in the art.

In another aspect of the technology, an assembly cap (or housing) 95 isdisposed atop a plurality of LED chips 30 configured on a singleflexible COB LED. In one aspect, the housing 95 is transparent andremains part of the lighting assembly. However in another aspect, theassembly cap or housing 95 is not transparent and is removed from thelighting assembly after further manufacturing steps are completed. Aluminescent coating 96, such as a phosphor coating, is deposited aboutthe interior of the assembly cap 95 and/or placed directly on the COBLED using some other fixture. The single luminescent (e.g., fluorescent)coating disposed about the assembly cap 95 covering a plurality of LEDchips 30 results in a uniform light pattern emanating from the entirearray. In one aspect, the luminescent coating 96 is applied after theCOB LED is configured in its arcuate shape as the coating hardens into arigid layer. Advantageously, when disposed in an arcuate fashion, theresult is a high-powered, compact, light source distributed over anarcuate surface. In contrast to a non-COB LED array, the flexible COBLED (or FCOB LED) array of the present technology provides high-power,uniform lighting options producing an output typically greater than 150lumens.

In one aspect of the technology, stiffening members (e.g., smalldiameter wires or thin polymer strips, etc.) are placed about the backside of the flexible substrate to increase the stiffness of the flexiblesubstrate but continue to permit the substrate to be malleable.Advantageously, the stiffening members help maintain the flexiblesubstrate in a selected configuration. For example, if the flexiblesubstrate is bent into an arc shape, the stiffening members maintain theflexible substrate in an arcuate shape. This feature minimizes thelikelihood that the bond between the flexible substrate and anunderlying heat sink will be disturbed. In addition, with specificreference to FIGS. 2-4, a flexible COB substrate 120 is disclosed havingwire leads 121 (i.e., circuit patterns) disposed within the substrate120 coupled to a plurality of bonding pads 122. The bonding pads areconfigured to receive an LED chip 30 thereon. In one aspect of thetechnology, the LED chip 30 are secured to the bonding pads by way of anadhesive or other means it is soldered to the positive and negativeleads on the bonding pads 122. A stiffening member 123 is secured to aback side 120 a of the substrate 120 behind the area where the LED chip30 is placed on the front side 120 b of the substrate 120. When theflexible COB substrate 120 is formed into an arcuate shape after the LEDchip 30 is bonded to the substrate 120, it is possible for stresses tobe placed on the soldering joints or other connecting joints between theLED chip 30 and the substrate 120. This can result in breakage of thejoint and failure of the product. The stiffening member 123 minimizesflexure of the substrate 120 in the area of the stiffening member 123while allowing flexure of the substrate 120 in the areas betweenadjacent stiffening members 123. Advantageously, the stresses on thejoints between the substrate 120 and LED chip 30 are minimized. In oneaspect, the stiffening member 123 comprises a rectangular, thinpolymeric material that extends from a first edge 124 of the substrateto a second edge 125 of the substrate. The stiffening member 123comprises a width that is at least as wide as the LED chip 30 and/or thearea where the LED chip 30 will be coupled to the substrate 120. In oneaspect, the stiffening member 123 comprises a heat-resistant polymericfilm that is adhered to the back side 120 a of the substrate 120.

In conventional lighting devices, light output losses associated withboth reflectors and lenses persist with a 4 to 12% loss of light eachtime a light beam passes through a lens or bounces off of a reflector.Expensive coatings on the lenses can reduce these losses to less than 2%per refraction/reflection, but these coatings may be cost prohibitive onlower priced consumer goods. In the example of a lantern, single ormultiple high brightness LEDs are projected up into a conical mirroredreflector to project the light into a 360 degree circle around thelantern. Alternatively, these same LEDs are projected upwards with thelight illuminating a “diffusing” tube of translucent or textured surfacein order to radiate light into a 360 degree circle. This configurationhas light losses of 12% and much greater and higher due toinefficiencies of light reflection off of the mirrored surface as wellas frequently projecting non-uniform light patterns. Furthermore, asingle point light source is considerably more brilliant than adistributed light source of the same lumen output making it moredifficult to observe directly without highly uncomfortable glare. Thisresults in the need for diffusers that intercept the light from thesingle point source and re-radiate from a much larger surface area inorder to reduce the “glare.” This is similar to the use of lampshades inhousehold lamps. The use of diffuser or lampshade will reduce the totallight output significantly with losses often greater than 50% of thetotal light source output. In an example of a headlamp, one or more LEDsmay be employed to provide overlapping circular patterns of light. Asingle LED will provide high brightness for a spot beam that giveslimited area lighting and often will provide two or more smaller outputLEDs that project overlapping areas of light for close up task lighting.The overlapping technique of projecting several light “spots” does notcreate a uniform field of light but rather circles of varying lightintensities, which is not optimal. In the example of bike headlights,one or more high brightness LEDs utilizing either a reflector or a totalinternal reflection (TIR) lens may be used to collimate the light into atight spot beam for distance with some peripheral light emitted in aconcentric cone for peripheral light. Typically this cone extends for 30to 45 degrees out from the line of sight of the spot beam. While thisworks well for aiding visibility for the rider, it does not provideeffective visibility of the rider by approaching cars or other threats.Various configurations attempt to divert some LED light through sideholes, add additional low power LEDs on the side or use polycarbonatelight pipers to divert light to the side of the rider. Tail-lights havesimilar limitations and attempt to divert light to the side byadditional LEDs, however this still leaves a number of “dark” angles ofapproach where the lights are not visible to oncoming threats. Aspectsof the current technology improve these deficiencies.

With reference to FIGS. 3a -3 c, in accordance with one aspect of thetechnology, a planar, linear FCOB LED strip 100 is formed into a 360degree ring and can be bonded to a 360 degree annular aluminum structurefor use in a lantern or flashlight, for example. In this aspect, theannular aluminum structure acts as the heat sink of the FCOB LEDstructure. An imaginary axis normal to a center of at least one of theplurality of LED chips 30 disposed on the strip 100 is disposed at anon-parallel angle with respect to an imaginary axis normal to a centerof an adjacent one of the plurality of LED chips 30, though in otherarrangements an imaginary axis normal to one of the LED chip 30 issubstantially parallel with an imaginary axis normal to an adjacent LEDchip 30. Selection of the LED chip 30 used in the FCOB LED arrayincludes the choice of illumination angles with respect to an axisnormal to the flexible substrate 10. In one aspect of the technology,the LED chip will project a substantially even concentration of lighthaving a conical projection of 120 degrees (e.g., 60 degrees off acentral axis of the LED chip). Because of the different conical shapesof the LED chips 30, the field of illumination of the different chips 30is necessarily different. However, in one aspect, the field ofillumination of at least one of the plurality of LED chips is differentthan the field of illumination of at an adjacent one of the plurality ofLED chips in that the primary field of illumination is directed in adifferent direction as an adjacent chip. Advantageously, the annularstructure of the FCOB LED provides for a consistent 360 illuminationwith LED chips 30 manufactured on a single substrate.

While specific reference is made to a strip 100 formed into asubstantially 360 degree shape, it is understood that numerous shapescan be formed. For example, in one aspect, a single planar flexiblesubstrate is disposed in an arcuate orientation forming an arc rangingfrom 120 to 180 degrees. A first plurality of LED chips 30 are mountedon a first arcuate substrate comprises a first lighting sub-assembly anda second plurality of LED chips mounted on a second arcuate substratecomprises a second lighting sub-assembly. The first and secondsub-assemblies each comprises a substantially 180-degree arc coupledtogether to form a substantially 360 degree ring. The first and secondsub-assemblies are powered by a single power source. However, power maybe provided selectively to each of the first and second sub-assembliesturning them on alternatively or together as desired.

In another aspect, a planar, linear FCOB LED strip (like that shown inFIG. 5a ) can be shaped to a 120 degree arc and bonded to a 120 degreeheat sink for wide illumination of a front facing task lighting. Forexample, FIG. 6 discloses a bicycle light 130 having a 120 degree arcFCOB LED light 131 disposed on a front thereof. Advantageously, thelight evenly illuminates the user's front and sides. In a bicycle lightapplication, for example, the front and sides of the bicycle areilluminated for high awareness of road hazards, animals, and otherpoints of interest. In addition, the biker has high visibility to alloncoming traffic within a full 180 degree arc (120 degrees of FCOB plus30 degrees on either side of each LED chip 30) in front with no darkspots/angles where an oncoming driver will not see the direct light ofthe FCOB LED. If combined with a similar red tail-light (i.e., theluminescent binder combines with the LED light to produce a red light)with a similarly shaped red FCOB LED, the biker will have complete 360degree visibility to all oncoming traffic. In one aspect of thetechnology, the FCOB LED is combined with a conventional spot beam LED132 (or other light sources) which will provide the longer distancelighting of a forward target. In one aspect, the spot beam 132 can betightly collimated into a brighter spot beam as the peripheral light isprovided by the FCOB LED 131. While reference to use with a bicycle isreferenced herein, it is understood that the FCOB LED array may be usedwith any number of products in any number of applications. For example,use as a headlamp, flashlight, lantern, headlight, lamp, and otherlighting applications are all contemplated herein. Generally speaking,by applying calculated geometries to the FCOB LED patterns, complexarcuate curves and angles can be obtained after mounting to theappropriate aluminum or other metal structures. In one aspect of thetechnology, where a FCOB LED is mounted onto a fixture having a 120degree arc, the resulting light will be radiated outwards for greaterthan 180 degrees of illumination. In another aspect of the technology,the FCOB LED is fabricated as a planar arc and then mounted onto afixture having a 120 degree arc with a 30 degree downward cant. Theresulting light pattern is a 180 degree horizontal illumination patternwith vertical light beginning upwards at 30 degrees and evenlydistributed downward to 90 degrees straight down.

In one aspect of the technology, with reference to FIGS. 7a -7 b, aplanar arc pattern of the FCOB LED can be bonded to a horizontallylocated conical (angled) semi-circle (or full circle) aluminum structureto yield a semi-circular (or full circle) light ring with a 45 degreedownward angled light. In this aspect, planar flexible substrate 150 isshaped to approximate a ring with an opening 153 through one side of thering, wherein opposing sides 151, 152 of the opening 153 through thering define a wedge-shaped opening. Thus arranged, the planar flexiblesubstrate 150 is disposed on a truncated cone-shaped heat sink 154creating a single annular assembly 155, wherein an imaginary axis normalto at least one of the LED chips 30 is not parallel to a planecorresponding with a bottom surface or a plane corresponding with a topsurface of the heat sink 154. In one aspect, when used in connectionwith a hand-held flashlight, the single annular assembly 155 is disposedon the flashlight in such a way that an imaginary axis normal to atleast one of the LED chips is not parallel or normal to a longitudinalaxis of the flashlight.

With reference now to FIGS. 8a through 8 c, a U-shaped FCOB LED 160 iscreated and disposed about a cylindrical heat sink 161. Similar to theFCOB LEDs referenced herein, a plurality of LEDs 162 are electricallycoupled together by wiring 163 on a flexible planar substrate. The FCOBLED 160 is conformable and bends about the radius of the cylindricalheat sink 161 to form a light device capable of projecting light in bothforward and lateral directions. While a cylindrical heat sink 160 isspecifically referenced, the U-shaped FCOB LED 160 may be disposed aboutany number of arcuate surfaces to create a number of different shapedlighting devices. Side portions 164, 165 of the U-shaped substrate aredisposed on opposing sides of the sink 161. However, depending on therelative size of the sink 161 and/or the specific geometry of theU-shaped substrate, the planar substrate is disposed about a cylindricalheat sink in a manner wherein an imaginary axis disposed normal to anLED chip on a first side 164 of the U-shaped substrate is not parallelwith an imaginary axis disposed normal to an LED chip on a second size165 of the U-shaped substrate.

In accordance with one aspect of the technology, the FCOB LED ismanufacturing through a series of steps. It is noted that no specificorder is required in these methods unless required by the claims setforth herein, though generally in some embodiments, the method steps canbe carried out sequentially. Broadly speaking, in accordance with oneaspect of the technology, a base plate is provided upon which anintermediate plate is disposed. The base plate is provided with guideposts that correspond to alignment holes placed within the intermediateplate. A flexible substrate is disposed atop the intermediate plate. Theflexible substrate likewise has alignment holes therein for placementabout guide posts within the base plate. A magnetic top plate isdisposed atop the flexible substrate. The magnetic top plate is alsoprovided with alignment holes corresponding to the guide posts disposedwithin the base plate. The base plate, intermediate plate, and top plateare referred to herein as the “plate assembly.”

A die (or LED chip) 30 is secured (via an adhesive or other means knownin the art) to the flexible substrate and cured. Once cured, the die issoldered to electrically conductive contact points afterwhich a resin isplace atop portions of the assembly. The assembly is then cured again.Once cured, the flexible substrate assembly is removed from the plateassembly. An arcuate heat sink is prepared with a conductive adhesiveabout a surface of the heat sink. Afterwards, the flexible substrateassembly is disposed about the arcuate heat sink. In one aspect, anarcuate cap or housing having an internal cavity shaped to approximatethe arcuate heat sink is prepared with a fluorescent binder wherein theflexible substrate/heat sink assembly is placed.

With reference now to FIGS. 9 through 23, in accordance with one aspectof the technology, a substantially planar metallic base plate 200 isprovided. The base plate comprises a plurality of guide posts 201 andalignment holes 202. A substantially planar intermediate plate 205 isdisposed atop the base plate 200. In accordance with one aspect of thetechnology, the intermediate plate 205 comprises a plurality ofalignment holes that correspond to the guide posts 201 of the baseplate. In this manner, the two plates are properly positioned withrespect to one another. As shown in FIGS. 11 and 12, a flexiblesubstrate subassembly 210 is disposed atop the intermediate plate 205.The subassembly 210 comprises a plurality of alignment holes 211 to beplaced over respective guide posts 201 of the base plate. The flexiblesubstrate subassembly 210 comprises a plurality of longitudinal flexibleprinted circuit boards (i.e., the flexible substrate) 212, each having aplurality of contact points 213 distributed evenly across a top surface214 of the printed circuit board 212. The contact points comprise aplurality of substantially oval contact points 215 each disposed above aplurality of circular contact points 216. The contact points 213 arearrayed about the printed circuit board 212 to permit placement of a dieor LED chip 30. In accordance with one aspect of the technology, theflexible printed circuit boards 212 comprise a tab 217 disposed aboutone side of the circuit board 212. Tab 217 comprises contact points 218and 219 for powering the circuit board 212 once fully assembled.

In accordance with one aspect of the technology, a substantially planarmagnetic top plate 220 is disposed atop the flexible substratesubassembly 210. The top plate 220 also comprises alignment holes 221configured to mate with post 201 to ensure proper alignment of theentire assembly. In addition to the alignment holes, the top plate 220comprises a plurality of apertures 222 corresponding substantially tothe dimensions of the flexible printed circuit boards 212. In thismanner, a working area is defined wherein LED chips 30 can be placed,soldering, placement of resin, and other curing procedures are conductedwithin the working area. The top plate 220 secures the flexible printedcircuit boards 210 within the plate assembly 225 to permit machineplacement of materials upon the flexible printed circuit boards 212 inthe working area.

With specific reference now to FIGS. 14-16, a die (or LED chip) 230 issecured to the oval contact point 215 with a heat transmissive adhesiveand the subassembly is cured at 150 degrees Celsius for approximately1.5 hours. A first connecting wire 231 is soldered to positive lead 231on the die 230 and the circular contact point 216. A second connectingwire 233 is soldered to negative lead 234 on the die 230 and the ovalcontact point 215. Resin is disposed atop the soldered subassembly afterwhich the subassembly is cured at 150 degrees for about 1.5 hours. Inaccordance with one aspect, the die and wire soldering are completedusing optically positioned instrumentation as is known in the art. Tab217 comprises leads 218 and 219 that are electrically coupled to the LEDchips 30 on the substrate 210 and are used to couple the assembly to apower source associated with an end product.

In accordance with one aspect of the technology, with reference now toFIGS. 17-23, an arcuate heat sink 240 is provided. In one aspect, thearcuate heat sink 240 comprises a metal ring, though numerous othershapes and arrangements are contemplated for use herein. The metal ring240 comprises a heat-transmissive adhesive 241 disposed about at least aportion of the ring. A flexible substrate subassembly 210, having theLED chips 30 soldered to contact pads and resin cured, is placed aboutthe exterior of the metal ring 240. In a preferred aspect, opposing endsof the flexible substrate 210 are adjacent one another when disposedabout the metal ring 240. The arcuate LED subassembly 250 can bedisposable within a transparent housing 260. The housing comprises aclear plastic, glass, polymer, or other suitable transparent materialand is shaped to approximate the arcuate LED subassembly 250. In thisaspect, the housing 260 is shaped to approximate a ring. The housing 260comprises a cavity 261 configured to receive the metal ring thereindefined by annular inner wall 263 and annular outer wall 264. An annulargroove 262 is disposed about a bottom of the cavity 261 for receiving anend of the LED subassembly 250 therein. In accordance with one aspect ofthe technology, a quantity of a luminescent binder (including, but notlimited to fluorescent binders) 270 is placed within the cavity 261 ofthe housing 260. A common yellow phosphor material is cerium-dopedyttrium aluminum garnet (Ce3+:YAG) though other materials may be used.The LED subassembly 250 is placed in the housing 260, either before orafter placement of the fluorescent binder 270. In one aspect, theinternal surface of the LED subassembly 250 is adjacent to the internalwall 262 of the inner ring of housing 260. The LED subassembly 250 andhousing 260 are sized such that when the LED subassembly 250 is placedwithin the housing 260, there is a space between the outer surface ofthe LED subassembly 250 and the internal wall of the housing 260. Inthis manner, the luminescent binder 270 is distributed about the entireinside surface of the outer wall 264 to assist in the distribution oflight about the entire outer surface of the housing. In one aspect ofthe technology, a vacuum is applied to the subassembly 250 and housing260 assembly in order to remove air pockets from the luminescent binder270.

While an annular shaped housing 260 has been described herein, it isunderstood that numerous shaped housing are contemplated for use hereinin order to accommodate any number of shapes of FCOB LEDs (includingthose shown in FIGS. 7 and 8, for example) and/or the housing 260 may beremoved after the luminescent binder 270 has set. Additionally, while asingle-piece housing has been shown, it is understood that a multi-piecehousing may be used in order to accommodate different geometries and/ordifferent applications. For example, in one non-limiting example, anL-shaped FCOB LED is disposed about a heat sink that requires the heatsink to be placed in a bottom portion of the housing with a top portioncoupled thereto after the FCOB LED is placed in the bottom portion. Inthis aspect, one or more apertures are located within the housing toallow for injection of the fluorescent binder. In an additional aspect,the housing may only partially encapsulate the FCOB LED. In onenon-limiting example, the FCOB LED may be placed on an arcuate heat sinkin such a manner that only the portion of the heat sink on which theFCOB LED is applied is intended to be encapsulated. That is, the surfacearea of the heat sink is larger than the FCOB LED. A housing intended tocover only the arcuate LED subassembly (i.e., the light producingflexible element) is mounted to the heat sink. A fluorescent binder ispre-applied to the housing and conforms to the surface of the arcuateLED subassembly during the mounting process.

Of course, it is to be understood that the above-described arrangementsare only illustrative of the application of the principles of thepresent invention. Numerous modifications and alternative arrangementsmay be devised by those skilled in the art without departing from thespirit and scope of the present invention and the appended claims areintended to cover such modifications and arrangements. Thus, while thepresent invention has been described above with particularity and detailin connection with what is presently deemed to be the most practical andpreferred embodiments of the invention, it will be apparent to those ofordinary skill in the art that numerous modifications, including, butnot limited to, variations in size, materials, shape, form, function andmanner of operation, assembly and use may be made without departing fromthe principles and concepts set forth herein.

1. A lighting device, comprising: a plurality of LED chips mounted on asingle planar flexible substrate, wherein the single planar flexiblesubstrate is disposed in an arcuate orientation and wherein each of theplurality of LED chips is powered by a single power source; a heat sinkhaving an arcuate surface shaped to approximate the arcuate orientationof the single planar flexible substrate and coupled to the flexiblesubstrate between complementary arcuate surfaces of the heat sink andthe flexible substrate; a luminescent coating disposed about a topsurface of the arcuate single planar flexible substrate; and a powersource coupled to the plurality of LED chips.
 2. The lighting device ofclaim 1, wherein the luminescent coating comprises a phosphor coatingthat encapsulates the plurality of LED chips disposed on the substrateand an entire top surface of the arcuate planar flexible substrate. 3.The lighting device of claim 1, wherein an imaginary axis normal to acenter of at least one of the plurality of LED chips is parallel to animaginary axis normal to a center of an adjacent one of the plurality ofLED chips.
 4. The lighting device of claim 1, wherein an imaginary axisnormal to a center of at least one of the plurality of LED chips is notparallel to an imaginary axis normal to a center of an adjacent one ofthe plurality of LED chips.
 5. The lighting device of claim 1, whereinthe field of illumination of at least one of the plurality of LED chipsis different than the field of illumination of at an adjacent one of theplurality of LED chips.
 6. The lighting device of claim 1, wherein thesingle planar flexible substrate is disposed in an arcuate orientationforming an arc ranging from 120 to 180 degrees.
 7. The lighting deviceof claim 1, wherein a first plurality of LED chips mounted on a firstarcuate substrate comprises a first lighting sub-assembly and a secondplurality of LED chips mounted on a second arcuate substrate comprises asecond lighting sub-assembly.
 8. The lighting device of claim 7, whereinthe first and second sub-assemblies each comprises a substantially180-degree arc coupled together to form a substantially 360 degree ring.9. The lighting device of claim 8, wherein the first and secondsub-assemblies are powered by a single power source.
 10. The lightingdevice of claim 9, wherein power may be provided selectively to each ofthe first and second sub-assemblies.
 11. The lighting device of claim 1,wherein the planar flexible substrate is rectangular.
 12. The lightingdevice of claim 1, wherein the planar flexible substrate is shaped toapproximate a ring with an opening through one side of the ring, whereinopposing sides of the opening through the ring define a wedge-shapedopening.
 13. The lighting device of claim 12, wherein the planarflexible substrate is disposed on a cone-shaped heat sink creating asingle annular assembly, wherein an imaginary axis normal to at leastone of the LED chips is not parallel to a plane corresponding with abottom surface of the heat sink.
 14. The lighting device of claim 12,wherein the planar flexible substrate is disposed on a truncatedcone-shaped heat sink creating a single annular assembly, wherein animaginary axis normal to at least one of the LED chips is not parallelto a plane corresponding with a top surface of the heat sink.
 15. Thelighting device of claim 12, further comprising a hand held flashlightwherein an imaginary axis normal to at least one of the LED chips is notparallel or normal to a longitudinal axis of the flashlight.
 16. Thelighting device of claim 1, wherein the planar substrate is shaped toapproximate a U shape.
 17. The lighting device of claim 16, wherein theplanar substrate is disposed about a cylindrical heat sink and whereinside portions of the U-shaped substrate are disposed on opposing sidesof the sink.
 18. The lighting device of claim 16, wherein the planarsubstrate is disposed about a cylindrical heat sink and wherein animaginary axis disposed normal to an LED chip on a first end of theU-shaped substrate is not parallel with an imaginary axis disposednormal to an LED chip on a second end of the U-shaped substrate.
 19. Thelighting device of claim 11, further comprising a plurality ofstiffening members disposed behind each of the LED chips.
 20. Thelighting device of claim 19, wherein the stiffening members comprise arectangular flexible material disposed about the back side of theflexible substrate.
 21. The lighting device of claim 20, wherein thestiffening members extend from a first end of the flexible substrate toa second edge of the flexible substrate.
 22. The lighting device ofclaim 19, wherein each of the stiffening members comprises a width thatis at least as great as the width of the LED chip.
 23. The lightingdevice of claim 19, wherein the stiffening members comprise a heatresistant polymer film.
 24. The lighting device of claim 1, furthercomprising a tab extending form a lateral side of the flexible polymersubstrate, said tab comprising an electrical coupling for coupling to apower source.
 25. The lighting device of claim 24, wherein the tab isnot covered by the luminescent coating.
 26. A lighting device,comprising: a plurality of LED chips mounted on a single planar flexiblesubstrate, wherein the single planar flexible substrate is disposed inan arcuate orientation and wherein each of the plurality of LED chips ispowered by a single power source; a rigid heat sink having an arcuatesurface shaped to approximate the arcuate orientation of the singleplanar flexible substrate and coupled to the flexible substrate betweenarcuate surfaces of the heat sink and the flexible substrate; aluminescent coating disposed about a surface of the arcuate singleplanar flexible substrate forming a rigid encapsulating layer about atop surface of the arcuate substrate; and a power source coupled to theplurality of LED chips.
 27. The lighting device of claim 26, furthercomprising a stiffener disposed behind each of the plurality of LEDchips about a back surface of the flexible substrate.
 28. The lightingdevice of claim 26, further comprising a tab extending laterally from aside edge of the flexible substrate.
 29. The lighting device of claim28, further comprising a transparent housing enclosing the flexiblesubstrate, heat sink, and coating.
 30. A method of manufacturing alighting device, comprising: (a) disposing an intermediate plate atop abase plate, wherein the base plate comprises guide posts that correspondto alignment holes placed within the intermediate plate; (b) disposing aflexible substrate assembly atop the intermediate plate, the flexiblesubstrate assembly comprising alignment holes for placement about guideposts of the base plate and further comprising a plurality ofrectangular flexible substrate strips removable from the flexiblesubstrate assembly, wherein each of the flexible substrate stripscomprises a plurality of wire bonding pads configured to receive a LEDchip thereon; (c) disposing a magnetic top plate atop the flexiblesubstrate, the magnetic top plate comprising alignment holescorresponding to the guide posts disposed within the base plate, whereinthe magnetic top plate further comprises apertures corresponding to atleast the wire bonding pads; and (d) securing a plurality of LED chipsabout each one of the plurality of flexible substrate strips.
 31. Themethod of claim 30, further comprising the step of removing the flexiblesubstrate assembly from intermediate plate and disposed a stiffeningmember about the back side of the flexible substrate behind each of theplurality of LED chips.
 32. The method of claim 31, arranging theflexible substrate in an arcuate shape and placing the flexiblesubstrate about an arcuate heat sink.
 33. The method of claim 32,further comprising placing the flexible substrate and arcuate heat sinkin an arcuate housing.
 34. The method of claim 33, further comprisingplacing a luminescent composition within the arcuate housing.
 35. Themethod of clam 34, further comprising applying a vacuum to the arcuatehousing to remove air bubbles from the luminescent composition.